Preheat the Oven: Set your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
Layer the Fruit: Pour the crushed pineapple (with juice) evenly into the baking dish. Spread the cherry pie filling on top.
Add the Cake Mix: Evenly sprinkle the dry cake mix over the fruit layer. Do not mix.
Drizzle Butter: Pour the melted butter over the cake mix, covering as much as possible. Sprinkle with chopped nuts and cinnamon if using.
Bake: Bake for 40-45 minutes, or until the top is golden brown and the fruit filling is bubbling.
Cool & Serve: Let the cake cool slightly before serving. Enjoy warm on its own or with a scoop of vanilla ice cream!